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From Dean Hiller <d...@alvazan.com>
Subject Re: question on setup for writes into 2 datacenters
Date Thu, 08 Sep 2011 21:09:35 GMT
thanks this is perfect...yeah, we want 4 nodes(2 in each data center) so
just a bit more than 3 ;) so we can have both datacenters be active at the
same time and not have to write to the other datacenter except in the
background.  This is perfect......hbase couldn't do this which I wanted
badly along with the in-memory write and write to disk in the background.
thanks!!!!
Dean

On Sun, Jul 24, 2011 at 4:40 PM, aaron morton <aaron@thelastpickle.com>wrote:

> Quick reminder, with RF == 2 the QUORUM is 2 as well. So when using
> LOCAL_QUORUM with RF 2+2 you will effectively be using LOCAL_ALL which may
> not be what you want. As De La Soul sang, 3 is the magic number for minimum
> fault tolerance (QUORUM is then 2).
>
> Cheers
>
>  -----------------
> Aaron Morton
> Freelance Cassandra Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 23 Jul 2011, at 10:04, Sameer Farooqui wrote:
>
> It sounds like what you're looking for is write consistency of
> local_quorum:
> http://www.datastax.com/docs/0.8/consistency/index#write-consistency
>
> local_quorum would mean the write has to be successful on a majority of
> nodes in DC1 (so 2) before it is considered successful.
>
> If you use just quorum write, it'll have to be committed to 3 replicas out
> of the 4 before it's considered successful.
>
>
>
>
> On Fri, Jul 22, 2011 at 1:57 PM, Dean Hiller <dean@alvazan.com> wrote:
>
>> Ideally, we would want to have a replication factor of 4, and a minimum
>> write consistency of 2 (which looking at the default in cassandra.yaml is to
>> memory first with asynch to disk...perfect so far!!!)
>>
>> Now, obviously, I can get the partitioner setup to make sure I get 2
>> replicas in each data center.  The next thing I would want to guarantee
>> however is that if a write came into datacenter 1, it would write to the two
>> nodes in datacenter 1 and asynchronously replicate to datacenter 2.  Is this
>> possible?  Does cassandra already handle that or is there something I could
>> do to get cassandra to do that?
>>
>> In this mode, I believe I can have both datacenters be live as well as be
>> backup for the other not wasting resources.
>>
>> thanks,
>> Dean
>>
>
>
>

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